Pneumatic transfer systems are finding increasing use in many areas, such as, for example, by banking institutions wherein such systems are used in conducting banking transactions between a bank teller and a remote customer. Documents and currency are transferred between the teller and customer in a pneumatically driven, generally cylindrical carrier through a tube connecting a teller terminal to a customer terminal.
Pneumatic transfer systems in present day use are generally of two types, i.e. captive carrier systems and non-captive carrier systems. Non-captive carrier systems are ones in which the carrier may be removed from the system to insert articles therein and to remove articles therefrom. Non-captive systems for banking applications typically utilize smaller carriers (approximately 4 inches in diameter and 10 inches in length) and smaller transfer tubes as compared to a captive carrier system which may have a carrier which is 8 inches in diameter and 15 inches in length. In this respect, the size and weight of the smaller carriers makes them more easily handled by customers, and therefore more than a larger carrier suitable for use in a non-captive carrier system. While such non-captive carriers are preferably small so as to be manageable by a customer, it is nevertheless desirable to maximize the load carrying capacity of such a carrier.
In this respect, the weight carrying capacity of any pneumatic transfer system is directly related to the ability of the system to establish and maintain air pressure or a vacuum therein, and this ability in many instances is related to the design of the system's blower assembly and to the pneumatic sealing capabilities of the system. Referring to the latter, it is typically the seal arrangement around the carrier access openings of the system's terminals which produces the greatest air leakage. In this respect, many recently developed non-captive, commercial pneumatic systems include terminals having a cylindrical housing which defines a "carrier receiver". The housing comprises or includes an extension of the transfer tube, which extension defines the carrier receiver. An opening in one side of the housing provides access into the transfer tube extension, i.e. the carrier receiver, for insertion and removal of the carrier. Such systems typically include either a hinged cylindrical door or a sliding cylindrical door for closing the access opening.
U.S. Pat. No. 4,913,598 discloses a non-captive system having a sliding cylindrical door for closing the access opening. As indicated above, a problem with such a design is providing a seal around the sliding door. In this respect, as will be appreciated, it is difficult to form a seal between two curved surfaces, especially if the pneumatic transfer system (as in U.S. Pat. No. 4,913,598) utilizes positive pressure to propel the carrier through the transfer tube, which positive pressure tends to force apart mating or joined components or surfaces.
The present invention overcomes this and other problems by providing a pneumatic transfer system for transferring a non-captive carrier between spaced-apart terminals through a transfer tube, which system includes a gate mechanism which closes and seals an access opening in a terminal along a generally planar surface, and which system utilizes vacuum pressure to propel the carrier and enhance the seal along the planar surface.